The Apps Learning Center template includes a demo training calendar where users can click a Google Apps training course to see its description and also link to a form for signing up. If you're offering Google Apps training, replace the demo with your own training calendar, and create a signup form of your own. This is all easy to do using Google Docs and Google Calendar.
Create a signup form in Google Docs
Create your training calendar
Embed the calendar in your site
View submitted form data in a Google spreadsheet